The present invention relates to a rotary bearing with a lubricant passage arrangement for supplying a lubricant both to engaging surfaces of a radially inner bearing part and a radially outer bearing part of a rotary bearing, and also to at least one further lubricating point.
The radially inner bearing part and the radially outer bearing part are rotatable relative to one another about an axis of the rotary bearing, and the lubricant passage arrangement includes at least one first lubricant passage with one end which opens into the inner peripheral surface of the radially outer bearing part and another end which is connectable with a lubricant supply, and a second lubricant passage which leads from the outer peripheral surface, of the radially inner bearing part leads to its inner peripheral surface and a ring chamber which is formed between the inner peripheral surface of the outer bearing part and the outer peripheral surface of the inner bearing part, with the first lubricant passage and the at least one second lubricant passage open in the ring chamber. Such a rotary bearing is disclosed for example in German patent document DE 195 19 770 A1.
A threaded spindle of a roller body threaded drive for a machine table is conventionally supported rotatably in a machine bed, and a threaded nut is fixedly connected with the machine table. When the machine table must move with a high speed along the threaded spindle, a correspondingly high rotary speed of the threaded spindle around its axis is required. The spindle rotary speed and thereby also a traveling speed of the machine table are however limited from above by the bending-critical rotary speed of the threaded spindle. For this reason at high machine table-traveling speeds frequently a construction with the fixedly arranged threaded spindle and rotatably arranged threaded unit is selected, as disclosed for example in the German patent document DE 195 19 770 A1.
In the embodiments shown in this patent the radially outer bearing part of the rotary bearing is formed as a special component fixedly connectable with the machine table, and furthermore the thread turns of the threaded nut of the threaded drive are provided on a radially inner peripheral surface of the radially inner bearing part. In other words the radially inner bearing part and the threaded part are formed of one piece with one another. As can be easily seen, for an orderly operation of the threaded drive disclosed in the document DE 195 19 770 A1 both lubrication of engaging surfaces between the radially outer and the radially inner bearing part is required, and also lubrication of the engaging surfaces between the threaded spindle and the threaded nut.
In order to provide the lubrication centrally from a stationary component which performs at least a rotary movement, the embodiments shown in the documents DE 195 19 770 A1 are united through a lubricant passage arrangement with a central lubricating supply point. A first lubricant passage extends from a central lubricant supply point with one end which opens at the inner peripheral surface of the radially outer bearing part in a ring chamber. The ring chamber is arranged between the radially outer and the radially inner bearing part and thereby can supply the engaging surfaces of both bearing parts with lubricant in a simple manner. For supplying the further lubricating point, namely the engaging points between the threaded nut and the threaded spindle, a second lubricant passage is provided which extends through the inner bearing part from its outer peripheral surface to its inner peripheral surface. The lubricant can be supplied from the radially inner end of this second lubricant passage in a simple manner to the engaging surface between the threaded nut and the threaded spindle.
In order to influence the lubricant distribution between the lubrication of the engaging surface of the rotary bearing and lubrication of the engaging surfaces between the threaded spindle and the threaded nut, the document DE 195 19 770 A1 discloses the embodiments shown in FIGS. 10, 11, and 12 with throttle elements at the inner peripheral surface of the radially outer bearing part and/or the outer peripheral surface of the radially inner bearing part. Depending on the properties of the lubricant to be used (lubricant grease or lubricant oil of different viscosity), a differently designed inner and outer bearing parts must be provided. This significantly limits the applications of the individual rotary bearings or individual threaded drives with rotary bearing-supported threaded nut, or a plurality of such a rotary bearings or threaded drives with rotary bearing-supported threaded nuts are needed.
Accordingly, it is an object of the present invention to provide a rotary bearing, in particular for a threaded drive with a rotary bearing-supported threaded nut, which avoids the disadvantages of the prior art.
More particularly, it is an object of the present invention to provide a rotary bearing, in particular for a threaded drive with a rotary bearing-supported threaded nut, which provides an efficient flexible adaptation of the rotary bearing or the threaded to the respective application conditions in particular the properties of the lubricant to be used.
In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention resides, briefly stated, in a rotary bearing of the above mentioned general type, in which in the ring chamber a lubricant distributing element is arranged as a special component, which is in a lubricant-supply connection with the at least one first lubricant passage, wherein at least one first outflow path is provided in and/or on the lubricant distributing element to supply lubricant to the engaging surfaces of the rotary bearing and wherein at least one second outflow path is provided in and/or on the lubricant supplying element, in order to supply lubricant through the at least one second lubricant passage to the at least one further lubricating point.
In accordance with the present invention the radially inner and the radially outer bearing parts can be formed as standard components. They however have to limit a ring chamber, so that the lubricant distributing element can be arranged in it as a separate component.
The lubricant distributing element defines a lubricant supply path whose throughgoing resistance for the lubricant can be selected in dependence on the desired lubricant distribution. In order to provide adaptation to the corresponding application conditions, in particular to the lubricant to be used, in accordance with the present invention it is sufficient to arrange the corresponding lubricant distributing element in the ring chamber of the standard rotary bearing.
When it is stated here that the lubricant distributing element xe2x80x9cdefinesxe2x80x9d the outflow paths, these means that these outflow paths singly and alone are formed by the lubricant distributing element, in particular are formed on it, for example in form of conveying openings whose diameter throttles the lubricant throughflow. Alternatively, the throttling action which controls the lubricant distribution can be provided by outflow paths which are formed between the lubricant distributing element and the surrounding wall surfaces, in particular of the ring chamber. Finally, it is also possible that one of the outflow path is formed throttlingly in the above mentioned manner, while the other outflow path does not provide any throttling resistance to the lubricant throughflow, but the lubricant is supplied to a throttling lubricant passage formed in one of the bearing parts of the rotary bearing.
When before or after for example the expressions xe2x80x9clubricant passagexe2x80x9d or xe2x80x9coutflow pathxe2x80x9d are utilized, this does not have to be construed as a limitation of the claims, but instead serves just for simplification of the explanation. In particular components which rotate around the axis can be associated with a plurality of corresponding types of lubricant passages of outflow paths, to guarantee a continuous lubricant supply.
The lubricant distribution element can be formed for example as a synthetic plastic component, in particular an injection molded part.
In a preferable embodiment of the invention, the lubricant distributing element can have a substantially U-shaped cross-section with two side legs and a connecting transverse web. At least one supply opening can be provided for example in the transverse web for supplying lubricant from the at least one first lubricant passage into the inner chamber of the lubricant distributing element which is limited by the transverse web and the both side legs of the U-shaped structure.
As explained above the first outflow path can be formed for example partially between one outer surface of the lubricant distributing element extending substantially orthogonal to the axial direction, and a counter surface of the ring chamber which also extends substantially orthogonal to the axial direction. This embodiment is especially recommended when the ring chamber is formed as a peripheral groove in the inner peripheral surface of the radially outer bearing part or/and the outer peripheral surface of the radially inner bearing part. The radius of the beginning of the surfaces, their distance, the length of the passage formed by these surfaces, and the viscosity of the lubricant, to mention just a few influences, determines the throughgoing resistance of the first outflow path.
The second outflow path can be formed for example so that the at least one second lubricant passage opens into the inner chamber of the lubricant distributing element. In this previously described case, the second outflow path does not contribute or only contribute insignificantly to throttling of the lubricant flow to the further lubricating point. Moreover, the flow resistance of the lubricant cloud leading to the further lubricant point is practically determined exclusively by the flow resistance of the second lubricant passage.
In accordance with a further embodiment of the present invention it is proposed to fix the lubricant distributing element on the radially outer bearing part, for example by means of at least one securing element, and in particular preferably both in an axial direction and in a circumferential direction. In a further embodiment of this variant of the invention, the securing element is formed by a pipe which is received in the first lubricant passage and engages in a securing depression provided on the outer periphery of the lubricant distributing element, wherein a bottom surface of the securing depression has a supply opening which leads to an inner chamber of the limit lubricant distributing element. It has the advantage that no additional openings which can influence the outer appearance of the rotary bearing must be provided for insertion of securing pins in the peripheral surface of the radially outer bearing part.
A radially inner end of the above mentioned pipe can engage in a portion of a stepped opening of the lubricant distributing element, which has a wider diameter. This stepped opening can form the supply opening of the lubricant distributing element, so that through the pipe and the stepped opening lubricant can be supplied into the inner chamber of the lubricant distributing element.
In a further embodiment of the present invention it is proposed to form the lubricant distributing element as a lubricant distributing ring. The term xe2x80x9cringxe2x80x9d is to be understood within the full range of its meaning and it is not limited only to a full ring extending over a whole peripheral length. In particular also split rings can be utilized. Also, the construction of the full ring is preferable both from operational and manufacturing reasons.
For example in order to arrange the lubricant distributing element in a simple manner in a peripheral groove of the inner bearing part, in accordance with a further embodiment of the present invention, the radially inner bearing part has two bearing part bodies which abut against one another with axial end surfaces. It is advantageous from manufacturing point of view, for example higher number of parts and lower prices, and from the point of view of bearing hole, when the both bearing part bodies are identical and mirror-symmetrical.
When in particular the radially inner bearing part of the inventive rotary bearing is not formed of one piece with the component on which the further lubricant point is arranged, or in other words contrary to the embodiments shown in the patent document DE 195 19 77 A1 it is not formed of one piece with the threaded nut of the threaded drive, it is advantageous when a ring groove is provided on the inner peripheral surface of the radially inner bearing part and extends preferably substantially over the whole periphery. It is then not necessary during the mounting of this component in the radially inner bearing part to pay attention to a predetermined relative orientation in the peripheral direction. It is further sufficient when the lubricant passages provided in this further component open into the ring groove. It is to be understood that additionally or alternatively a further such ring groove can be provided on the peripheral surface of the further component, or in other words for example on the threaded nut.
The inventive rotary bearing can be formed for example as a roller bearing and preferably as a roller bearing with at least two rows of rolling bodies spaced from one another in an axial direction. It is further advantageous when the load lines of the both rolling body rows enclose an acute angle with the axis, and the load lines of the both roller body rows form preferably an O-arrangement in a section which contains the axis. In other words it is advantageous when a two-row inclined rolling body bearing is used in the O-arrangement.
The tilting safety of the inventive rotary bearing around a turning axes which extends orthogonally to the rotary bearing axis can be improved when the axial distance between both rolling body rows is smaller than the diameter of the rolling bodies rows, preferably smaller than 0.8 time, but preferably amounts to at least 0.5 times of this diameter, for example substantially 0.3 times of this diameter. The same tilting safety is possible when the rotary bearing is formed axially shorter, as for example for the known roller bearings in the document DE 195 19 770 A1. The axial distance between both roller bearing rows is measured from a roller body center to a roller body center of two roller bodies located in the same peripheral position. Analogously this is also true for the diameters of the roller body rows. Since this embodiment variants improve the properties of the inventive roller bearing independently from providing of a special lubricant distributing element, for this variance a separate protection is sought.
The both roller body rollers can have a diameter of for example substantially 65 mm. Moreover, it is advantageous when the roller bodies are guided in the roller body cages and are held there. Finally, the roller bodies can be formed as balls, rollers, and the like.
The present invention deals also with a threaded drive with a threaded spindle, a threaded nut which threadingly engages with the threaded spindle, and a rotary bearing with a radially inner bearing part and a radially outer bearing part which are rotatable relative to one another about an axis of the roller bearing and radially limit a ring chamber, a lubricant passage arrangement for supplying lubricant both to the engaging surfaces of the rotary bearing and also to the engaging surfaces of the threaded spindle and the threaded nut, wherein the lubricant passage arrangement has at least one first lubricant passage with one end opening at the inner peripheral surface of the outer bearing part in the ring chamber and with another end connectable with a lubricant supply, and a second lubricant passage which leads to the outer peripheral surface of the inner bearing part from the ring chamber, wherein the threaded nut and the radially inner bearing part of the roller bearing are formed as separate components and which during the mounting of the threaded drive are mountable on one another, and wherein in the threaded nut at least one third lubricant passage is formed which is in a lubricant-supply connection with the second lubricant passage.
This threaded drive is different from the threaded drives disclosed in the document DE 195 19 770 A1 first of all in that the threaded nut and the radially inner bearing part of the rotary bearing as formed as separate components. This simplifies the manufacture of the threaded drive since for providing a threaded drive with rotatable threaded nuts both for the manufacture of the rotary bearing and also for the manufacture of the threaded drive itself, the separate conventional techniques can be utilized and no compromise for the manufacture of the threaded nut or the radially inner bearing part of the rotary bearing must be made.
It is to be understood that in this threaded drive preferably the above described rotary bearing can be utilized, so that with respect to further modifications the explanations of the inventive rotary bearing can be dispensed with.
Lubricant oil can be preferably used as a lubricant for high rotary speeds or traveling speeds of the machine table. However, the lubricating grease is not excluded as well.
In accordance with a further aspect of the invention, a threaded drive is proposed which includes a spindle with a spindle axis, a nut which is in a threaded engagement with a spindle, a rotary bearing with two bearing parts which are centrally arranged with one another relative to the spindle axis and are rotatable relative to one another around the spindle axis and limit a ring chamber therebetween, with the radially inner bearing part connected or connectable non-rotatably with the nut, and a lubricant supplying system for supplying the bearing engaging surfaces of both bearing parts and the threaded engaging surfaces of the spindle and the nut with lubricant, wherein at least one lubricant supplying path of the lubricant supplying system which is supplied from a lubricant source with lubricant leads through the radially outer bearing part to the ring chamber and there branches into at least two branching paths, from which at least one first branching path leads into the ring chamber to at least one part of the bearing engaging surfaces and the at least one second branching path leads through the radially inner bearing part to the at least one part of the threaded engaging surfaces.
In accordance with the present invention in such a threaded drive it is provided that the at least one of the two branching paths has a controllable throttling point.
The provision of the controllable throttling point allows a control of the feed of lubricant to the bearing engaging surfaces and/or the threaded engaging surfaces.
In particular, by changing the opening cross-section of the throttling point the ratio between lubricant quantities fed through the both outflow paths can be influenced. For this purpose, it is especially advantageous when the throttling point is formed as a controllable blocking point, which is adjustable between an opening position in which it provides the throughflow of lubricant and a closing position in which the throughflow of lubricant is substantially interrupted. In this way it is possible when necessary to provide the lubricant feeding at least temporarily completely in one of the outflow paths. This can be especially advantageous when a post lubricant consumption takes place only on the bearing engaging surfaces or only on the threaded engaging surfaces.
Preferably the opening cross-section of the throttling point is controllable in dependence on the lubricant pressure in the lubricant supply path, in particular with the use of lubricating grease as a lubricant, so that in a simple manner via the lubricant pressure in the lubricant supply path the ratio of the lubricant quantities can be determined which are supplied to the bearing engaging surfaces and the threaded engaging surfaces. In practice it has been shown that the lubricant consumption at the threaded engaging surfaces is frequently greater than at the bearing engaging surfaces. As a result the lubricant supply for lubrication of the threaded engaging surfaces can be already used up, while for lubrication of the bearing engaging surfaces in the first outflow path lubricant is still available. When then a post filling of the lubricant supply system with fresh lubricant is performed, it is desired that this fresh lubricant predominantly is supplied or exclusively is supplied into the second outflow path to avoid an oversupply of the bearing engaging surfaces.
In a preferable embodiment of the invention for the controllable throttling point, the throttling point is arranged in the first outflow path and its opening cross-section is smaller at a higher lubricant pressure in the lubricant supply branch and is greater at a lower lubricant pressure.
For realization of throttling point, the radially outer bearing part can carry a ring tongue which is provided at the inner peripheral side, extends into the ring chamber and is flexibly deflectable. The throttling point is formed between one of the tongue side surfaces and a throttle limiting surface formed on the outer peripheral side of the radially inner bearing part, and the ring tongue limits the lubricant supply path at its opposite tongue side surface. Depending on how high is the lubricant pressure in the lubricant supply path, in this embodiment the ring tongue is deviated more or less to the throttle limiting surface, which corresponds to a greater or smaller narrowing of the throttling point. The ring tongue can be produced of the same material with the outer bearing part as a one piece. Alternatively, it can be formed separately from the outer bearing part. In particular the ring tongue can be formed by one of the U legs of the lubricant distributing ring which has an approximately U-shaped cross-section, as described above. Each of the legs of this distributing ring can form a flexible ring tongue. It is to be understood that the aspect of the controllable throttling point is not dependent on whether the nut is formed of one piece with the radially inner bearing part or is formed as a separate component.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.